Description:
------------
Memory leak when running unbuffered queries in PDO with ATTR_EMULATE_PREPARES set to false.

Test script:
---------------
<?php
ini_set('memory_limit', '16M');

$pdo = new PDO('mysql:host=*;dbname=*', '*', '*');
$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$pdo->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, false);

$result = $pdo->query("SELECT * FROM large_table");

foreach ($result as $i => $row)
    if ($i % 10000 === 0)
        printf("%10s %10s\n", $i, memory_get_usage());

Expected result:
----------------
consistent memory usage, eg:

         0     2097152
     10000     2097152
     20000     2097152
     30000     2097152
     40000     2097152

Actual result:
--------------
         0    2097152
     10000    4194304
     20000    8388608
     30000    12582912
     40000    14680064

Fatal error: Allowed memory size of 16777216 bytes exhausted (tried to allocate 16384 bytes) in /php on line 10